Net income for the fourth quarter fell 47 percent to $48 million on revenue of $490 million. When adjusted to remove the effect of an interest rate hedge and expenses relating to the sale of a retail division, the company earned 48 cents per share for the quarter.

Analysts polled by FactSet expected the company to earn an adjusted 44 cents per share on sales of $423 million.

A boom in U.S. natural gas production and mild winter temperatures that reduced heating demand have increased supplies of natural gas, and lowered prices.

For the quarter, the company's revenue per thousand cubic feet of gas fell 16 percent from $5.22 to $4.39. For the full year, average prices fell 21 percent, the company said.

Company revenue for the year was flat compared with 2011 at $1.6 billion. The company's net income fell 62 percent to $183 million. The company's results were inflated in 2011, however, because of sales of a pipeline and processing center.

After adjusting for these one-time items, the company's per share earnings fell 32 percent to $1.49, from $2.19.

But for the year the company's natural gas production rose 33 percent to a record 256 billion cubic feet, driven by an 85 percent increase in production from the Marcellus shale in Pennsylvania.

The company's proved reserves of natural gas — an important indication of what the company can hope to produce in the future — increased 12 percent to 6 trillion cubic feet.